Will the new runways be parallel to the present 07-25 or some other heading? Looking at Google maps, the only immediately available space is for parallel runways.

Yes - you can see the construction on Google Maps just north of the current complex. They started demolishing buildings a year or so ago and now there's quite a lot of earthmoving on. There's an expressway currently cutting across the expansion area, but it's being rerouted (also visible on Google). The new terminal complex will be midfield, between the parallel runways.

Unsure if the current terminals will stay in service or not - many other Chinese airports have opened large new terminals recently that have completely replaced the old buildings. Tianjin turned their old terminal into a corporate jet center, Zhengzhou turned theirs into a convention hall. Wuhan and Shenyang's old terminals are connected to the new buildings, but are currently closed off and will only reopen when traffic justifies. Shenzhen will tear their old terminals down. Guiyang remodeled their old terminal to match the new one, and integrated it with the new complex. So it's anybody's guess, really.